Which of the following best describes photovoltaic cells?

Photovoltaic cells are devices specifically designed to convert sunlight into electricity through the photovoltaic effect. When sunlight strikes the surface of these cells, it excites electrons, generating a flow of electric current. This direct conversion process is the fundamental principle behind how solar panels work, making them a crucial technology for harnessing solar energy.

The other options refer to different functions not associated with photovoltaic cells. Filtering sunlight would pertain to optical devices like filters or lenses, while converting electrical energy into light relates to light-emitting diodes (LEDs) or other light sources. Regulating temperature is more aligned with thermal management systems, not with energy conversion like what photovoltaic cells achieve. Thus, the best description of photovoltaic cells is that they convert sunlight directly into electricity.